1. Field of the Invention
This invention relates to catheters used for the introduction of fluids or electrical leads into a patient. More particularly, it relates to an improved catheter and method for relieving stress at an external lead portion of a catheter, which is inserted into a patient through an implanted percutaneous access device.
2. Prior Art
Various flexible percutaneous leads have been employed in the past which extend into the body of a patient and exit the patient's body at some selected location on the body. Such leads include, for example, electrically conductive temporary or permanent heart pacer leads and neural stimulator leads for stimulating the nervous system of the patient. One end of such lead, the end in the patient's body, is located at the location which is to be stimulated--for example, the myocardium or the epidural space surrounding the spinal cord. The conductive lead is connected to a stimulator which may be carried on the exterior of the patient's body. The stimulator produces electrical signals which are transmitted through the lead to stimulate the tissue which is to be stimulated deep within the patient's body.
Problems have been encountered with such percutaneous leads which have been fixed in place at the location at which the lead exits the skin. One such problem is that the strain which may be imparted to the lead during patient activity are transmitted to the exit location and may cause movement or displacement of the lead and even tearing of skin with attendant patient trauma. U.S. Pat. No. 4,579,120, entitled "Strain Relief for Percutaneous Lead" teaches a method and member for anchoring and relieving the strain on such leads. The stress toward which that invention is directed is stress to the patient at the exit site, most particularly stress caused by the movement of a sutured percutaneous lead.
Whereas the function of electrically conductive leads is not inhibited by bending and kinking, catheters which are used to transmit fluids have an internal lumen which must allow unimpeded fluid flow. Cracks in a catheter which transmits fluid will allow fluid to leak out and air to leak in; similar cracks in electrical leads are much less problematic. Accordingly, the disclosure of U.S. Pat. No. 4,579,120 is much less useful for catheters leads because no method is provided for preserving the integrity of the inner lumen of a hollow catheter.
Other percutaneous access devices (PADs) are known which are more specifically designed for catheter support. Nevertheless, such PADs alone are not adequately suited for preventing damage to known catheters, or even for preventing compromise of the integrity of internal catheter lumens, because catheter damage often occurs at the leading external edge of the catheter, beyond the PAD itself. The weight of the catheter or external forces act on the catheter and can cause the catheter to place strain on the PAD. Such forces are likely to lead to bending, kinking, or cracking of the catheter near the entry site impeding fluid flow, and can also lead to injury to the patient.
Some solutions to the above-discussed catheter problems have been proposed. It is known, for example, to place an approximately ninety degree bend in catheters to alleviate strain. U.S. Pat. No. 4,419,094 entitled "Suprapubic Catheter System" discloses a catheter with a curve in it. The catheter is held in place in a fixed direction and in a curved conformation by means of a plate which is attached to a second plate which, in turn, may be sutured or taped to the patient. It would, of course, be preferable to have a catheter for use with a PAD which does not require additional sutures o adhesives, which does not require a plate assembly, and which is capable of being adapted for use in any direction. Such a catheter is disclosed in U.S. Pat. No. 4,886,502 entitled "Peritoneal Access Catheter", the teaching of which is incorporated herein by reference, in which a flexible bellows section was implemented to allow a catheter to adopt up to a ninety degree bend in any direction.